Bulkhead doors are well known on naval vessels. As used herein, “bulkhead door” should be taken to mean a sealable door installed in a vertical surface (bulkhead door), horizontal surface (“hatch cover”), or a door-within-a-door (“scuttle”). A typical prior art bulkhead door includes a resilient gasket that mates with an edge of a collar surrounding a bulkhead opening and extending from the bulkhead outer surface. In sealing use of a bulkhead door, a plurality of pivotable latches, known in the art as “dogs”, are mounted on the bulkhead and may be pivoted into position against the outer surface of the door where they progressively engage wedged elements, known in the art as “strikers”. Such progressive engagement causes the gasket to be compressed against the collar edge, sealing the bulkhead opening against water and/or gas transmission.
Prior art bulkhead doors have several disadvantages. Such doors typically are formed of sheet steel and are relatively heavy, for example, about 125 pounds. Navy regulations require that a door or hatch cover may require no more than a maximum of 50 pounds of force to open; thus, many doors and hatches require helper springs to partially offset the weight of a steel door.
Being formed of steel, prior art doors are vulnerable to rust, especially under saltwater exposure, requiring that the lower door edges and gasket channels be reconstructed relatively often, requiring welding and grinding. Prior art inventoried doors also tend to be inconsistent in their manufacture. Thus each door must be custom-fitted to its respective bulkhead opening to assure watertight and gastight sealing performance, which fitting typically requires grinding and/or welding (“hot work”) and is a generally “dirty” operation. When hot work or an open flame is required during maintenance of a vessel, naval regulations require a large force of fire security personnel to be present not only on the deck on which the work is conducted but also on the decks immediately above and below the work. The Navy estimates that 1000 manhours are required for maintenance of a single door during the service life of a vessel.
Prior art doors typically are formed by stamping from sheet metal and include a stamped relief pattern to enhance flexural rigidity. It has been found that such a pattern is highly undesirable, for two reasons: first, the pattern greatly increases radar reflection from the door, thus aiding an enemy; and second, the pattern is difficult to wash down easily and thoroughly as may be required for washdown of a chemical spill or biochemical attack. For these considerations, a smooth surface is preferred.
Typically, many of the bulkhead openings in a ship are identical in height, width, and shape. However, a ship typically is outfitted with a mixture of left-hinge and right-hinge bulkhead openings, requiring doors having corresponding right- and left-oriented hinge blades and door handles. Further, the openings may vary between 2 and 10 in the number of dogs provided for engaging a bulkhead door, requiring an equivalent number and placement of strikers on the door. Thus, in the prior art, although bulkhead openings may be identical, the required doors are not. Therefore, a naval vessel carries an extensive, expensive, and heavy inventory of spare doors to cover all possible replacement contingencies.
This cumbersome inventory is made worse by the need on many ships to cover a variety of naval door opening sizes, for example, 26×66 inches and 26×63 inches, both left and right hinged, each with possibly 3, 6, 8, or 10 dogs; and 18×36 inches, both left and right hinged (a scuttle door), having 2, 4, or 6 dogs.
Further, in prior art bulkhead doors, the resilient gasket is not well-captured by the door and require adhesives for retention in a gasket channel. Further, the gasket is exposed to attack by fire, which can result in sealing failure of the door. Further, replacement of a deteriorated gasket requires laborious and time-consuming scraping off of the old gasket and adhesives and re-preparation of the door surface for receiving the new gasket and adhesive.
What is needed in the art is a universal bulkhead door that eliminates exposed metal dogs on the exterior of the door, has a smooth surface on both the interior and exterior of the door, provides consistent lockdown pressure across the door, shields the door gasket from attack by fire, is readily and cleanly washed down, may be opened easily without helper springs in a hatch mode, provides for simple replacement of a door gasket, and may itself be easily replaced without requiring hot work.
It is a principal object of the present invention to reduce the inventory of spare bulkhead doors which must be carried on a naval vessel.
It is a further object of the invention to reduce the weight of a bulkhead door.
It is a still further object of the invention to protect a bulkhead door gasket from exposure to fire.
It is a still further object of the invention to simplify replacement of a bulkhead door gasket.